Improve DCE of dead parts of a permute chain

gcc.dg/vect/bb-slp-pr78205.c is reported to have regressed with
the PR113073 change and in the end it's due to the DCE performed
by vect_transform_slp_perm_load_1 being imperfect.  The following
enhances it to also cover the CTOR and VIEW_CONVERT operations that
might be involved.

	* tree-vect-slp.cc (vect_transform_slp_perm_load_1): Also handle
	CTOR and VIEW_CONVERT up to the load when performing chain DCE.

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index a82fca451610e5bb3aef2e864f98a4291590d280..1a357cb7549a6c68042907fd1e63ad57c745a60b 100644 (file)
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -8634,10 +8634,21 @@ vect_transform_slp_perm_load_1 (vec_info *vinfo, slp_tree node,
     for (unsigned i = 0; i < dr_chain.length (); ++i)
       if (!bitmap_bit_p (used_defs, i))
        {
-         gimple *stmt = SSA_NAME_DEF_STMT (dr_chain[i]);
-         gimple_stmt_iterator rgsi = gsi_for_stmt (stmt);
-         gsi_remove (&rgsi, true);
-         release_defs (stmt);
+         tree def = dr_chain[i];
+         do
+           {
+             gimple *stmt = SSA_NAME_DEF_STMT (def);
+             if (is_gimple_assign (stmt)
+                 && (gimple_assign_rhs_code (stmt) == VIEW_CONVERT_EXPR
+                     || gimple_assign_rhs_code (stmt) == CONSTRUCTOR))
+               def = single_ssa_tree_operand (stmt, SSA_OP_USE);
+             else
+               def = NULL;
+             gimple_stmt_iterator rgsi = gsi_for_stmt (stmt);
+             gsi_remove (&rgsi, true);
+             release_defs (stmt);
+           }
+         while (def);
        }
 
   return true;